P-related peptides [VIP-related peptides [VIP, PACAP] have widespread effects in the gastrointestinal tract (GI) and central nervous system affecting such diverse functions as motility, secretion and growth of normal and neoplastic tissues. The actions of VIP-PACAP-related peptides is mediated by three receptors (VIP-1-R, VIP-2-R, PACAP-R). Studies in this project are aimed at understanding the molecular basis of action of these different receptors and at developing selective ligands that function as selecting agonists or antagonists at these different receptors. In general, two groups of studies are being performed in this project. To define the pharmacology of VIP receptors, the rat and human VIP-1-R and VIP-2-R receptors have been cloned and stably transfected in CHO and PANC1 cells. Furthermore, various native cells were screened by RT-PCR, Northern blots and binding studies to identify cell lines that have only one native VIP-R subtype. The breast cancer cell line, T47D was found to possess predominantly hVIP-R and to possess sufficient numbers of receptors to be useful for pharmacology and cell biology studies. The VIP pharmacophore is being determined for each VIP-R subtype by alanine and D-amino acid screening, to attempt to identify selective ligands. It has now been completed for the rat and human VIP-1-R and the results are now being analyzed. As a result of this study a simplified analogue of VIP with 11 alanines with potency equal to VIP has been made. This simplified VIP analogue will be an excellent template for future studies. Secondly, to study the molecular basis for ligand internalization by VIP related receptors, receptor mutants with varying lengths of COOH terminus deletions are now being made. It is planned to compare the effect of the mutations in the VIP- 1-R and VIP-2-R on internalization of ligand, receptor coupling and affinity for ligands. - vasoactive intestinal peptides